# GENERATE THE BOARD

my @board;
my $inversions;
GEN:
@board = (0, shuffle(1..15));
# @board = (1,0,2..15); # for testing
$inversions = 0;
for my $a(1..15) {
  for my $b(1..15) {
    ++$inversions if($a<$b and $board[$a]>$board[$b])
  }
}
goto GEN if $inversions % 2;

##</code><code>##

my @board;
my $inversions = 1;
while ($inversions % 2) {
    @board = (0, shuffle(1..15));
    $inversions = 0;
    for my $x (1 .. 15) {
        for my $y ($x + 1 .. 15) {
            $inversions++ if $board[$x] > $board[$y];
        }
    }
}